Impact absorbers of this type are known, for example, from DE 34 19 165 A1, in which impact absorbers are described that comprise two tubes that are displaceable one inside the other, wherein an inner tube, which is closed towards the outside, has a gas space, which is provided with a gas filling, which is under high pressure. A first liquid space, which is separated from the gas space by a separating piston, is likewise located in the inner tube. Moreover, a throttle element in the form of a disk with a throttling opening, which hydraulically connects the first liquid space to a second liquid space, is located in the inner tube. If an impact absorber is to absorb impact forces, which develop especially in a collision of a motor vehicle with an obstacle, the inner tube immerses into the outer tube. The hydraulic fluid located in the second liquid space is now displaced through the throttling opening into the first liquid space, and the gas cushion located in the gas space above the separating piston is compressed at the same time. The increase in volume in the first liquid space takes place, by contrast, against the force of a gas space forming a gas spring, which is additionally pretensioned as a result. The pretension of the gas spring, generated during the immersion of the inner tube into the outer tube, brings about the return of the impact absorber into the starting position as soon as the forces acting on the inner tube from the outside no longer act. The absorption of the impact forces takes place without permanent damage to the impact absorber at impact velocities of up to about 8 km/hour. The energy is dissipated by a deformation piston at higher impact velocities in the impact absorber disclosed in the above-mentioned document. The energy is dissipated due to the widening of the outer tube in the axial direction. Such an impact absorber, which is preferably attached to rigid carrier parts of the vehicle in automotive engineering, acts nearly as a rigid unit because of the absorbing force acting as a function of the velocity. A path limitation is provided to allow the crumple zone of the vehicle to become active in this case.